Catalyst regeneration using solvent washes is known to the industry.
Japanese patent publication J6 1271035 teaches the regeneration of used catalyst in the hydrogenation of coal tar pitch by washing with aromatic solvent, drying with inert gas and washing with water. The washing uses as the aromatic solvent a middle oil, washing oil, anthracene oil, methyl naphthalene oil, quinoline oil, etc. at a temperature of 100 to 450.degree. C. in the presence of hydrogen at 50 to 250 kg/cm.sup.2. Any solvent adsorbed by the catalyst is removed by an inert gas strip, e.g. Nitrogen at 100 to 400.degree. C. at a gas hourly space velocity of 100-5000. The water washing removes water soluble alkali metals from the catalyst. The catalysts which are reactivated include hydrogenation active metals supported on porous inorganic oxides, e.g. alpha alumina, silica, magnesia, zeolite, kaolin. Hydrogenation active metals are copper, vanadium, molybdenum, tungsten, cobalt, nickel and iron, etc.
Japanese patent publication J6 2282645 teaches the regeneration of supported palladium hydrogenation catalysts by washing with an aromatic hydrocarbon. The catalyst is used to hydrogenate dienes. The aromatic solvent used to wash the catalyst is preferably benzene, toluene, xylenes, mesitylene, ethyl benzene, o-, m-, and p- di ethyl benzene, cumene, o-, m-, and p- di isopropylbenzene, tert-butyl benzene and/or amylbenzene, etc .